Crystal grow

At equilibrium, crystal growth and dissolving rates become equal, and the process of Ostwald ripening may now appear, in which the larger crystals grow at the expense of the smaller ones. The kinetics of the process has been studied (see Ref. 103). 

Either pure aqueous or aqueous/solvent solutions work. It is entirely up to the preference of the chemist as to which one they use. Just to make one feel more secure, there is a little test one can do with the bisulfite solution to see if they got it right. Just put a little of that ketone known as acetone into the saturated solution and watch the crystals grow. Isn t it nice how chemistry works ... 

The polycrystaUine EGS is converted to siagle-crystal silicon via the C2okralski (CZ) crystal growing process, based on the solidification of silicon atoms from the Hquid phase at a moving iaterface. Volume production of 200-mm diameter crystals is standard. Development of crystals having diameters of up to 400 mm has been predicted (3). 

Oxygen also dissolves in the silicon crystal lattice, forming SiO which may radically affect the electrical properties of the silicon. Oxygen is usually unintentionally introduced during the crystal-growing operation in concentrations up to the solubility limit (ca 2.5 x 10 atoms/cm ). When... 

Nucleation is initiated by secondary mechanisms involving the seed crystals or low super-saturation and high surface area of seed crystals eliminate or minimize nucleation seed crystals grow... 

Seed crystals grow and participate in secondary nucleation by contact mechanisms throughout run... 

In advancing-front or layer melt crystallizations, mother Hquor flows over a cooled surface on which material is crystallized. The advancing front of crystals grows in the direction from the cooled surface into the mother Hquor. A variety of techniques can be used to take advantage of this type of Operation. 

Columnar crystals growing into solution from mould walls... 

Equiaxed crystals growing from solution in mould centre... 

Stephen Keith, a historian of science, has examined the development of this parepisteme (Keith 1998), complete with the stops and starts caused by fierce competition between individuals and the discouragement of some of them, while a shorter account of the evolution of crystal-growing skill can be found in the first... 

Holden, A., and P. Morrison, Crystals and Crystal Growing. Cambridge, Mass., The MIT Press, 1982... 

S. R. Coriell, B. T. Murray, A. A. Chernov, G. B. McFadden. Step bunching on a vicinal face of a crystal growing in a flowing solution. J Cryst Growth 169 773, 1996. 

The crystal compositions vary, depending on the transport agent used, from TiB,4,y (Ij) and TiBj <,4 (TeCl4). At process temperatures > 1000°C and with I2, the transport direction is reversed. Crystals grow in the cold zone of the tube, but only microscopic needle-like crystals are obtained. ... 

The crystal grows when a supply of powdered raw material is dropped through the flame onto the molten surface. The powder is added to the flame from a screen, which is tapped intermittently. 

The various sohd sulfur allotropes are all more or less yellow at 20 °C but the scale ranges from the deep orange-yellow of to the pale yellow of S. The color also depends on the particle size As finer the particles as lighter the color impression. Chemically produced Ss has in fact occasionally been obtained as a colorless material at room temperature which only slowly turns yellow as the initially tiny crystals grow [61]. The sample temperature is also of decisive influence (thermochromic effect) [10] (see above). 

However, if one desires a large sdngle-ciystal, then the methods needed to grow it differ considerably. This is the subject of this Chapter. We will examine crystal-growing methods and the equipment needed to do so. We will then examine the different t5q>e of ciystals used both as sensors and as the basis of specific devices used in the electronics industry. 

The Czochralski Method has remained the most frequently employed method for obtaining single crystals. The seemingly formidable complexities involved have been conquered by the use of computer-control of the crystal-growing Parameters. One such system, available commercially, is shown in 6.4.12. (on the next page). 

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